Search results
Results From The WOW.Com Content Network
2.1 Measurement of Earth's circumference. 2.2 ... instance of many terms still ... estimation of radius and circumference of Earth Archived 2020-01 ...
Treating the Earth as a sphere, its circumference would be its single most important measurement. [2] The first known scientific measurement and calculation was done by Eratosthenes, by comparing altitudes of the mid-day sun at two places a known north–south distance apart. [3] He achieved a great degree of precision in his computation. [4]
Eratosthenes (c. 276 – c. 194/195 BC), a Greek mathematician who calculated the circumference of the Earth and also the distance from the Earth to the Sun. Hipparchus (c. 190 – c. 120 BC), a Greek mathematician who measured the radii of the Sun and the Moon as well as their distances from the Earth. On the Sizes and Distances
Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
He measured the Earth's circumference by reference to the position of the star Canopus. His measure of 240,000 stadia translates to 24,000 miles (39,000 km), close to the actual circumference of 24,901 miles (40,074 km). [11] He was informed in his approach by Eratosthenes, who a century earlier used the elevation of the Sun at different latitudes.
Posidonius's method for calculating the circumference of the Earth, relied on the altitude of the star Canopus. Posidonius was informed in his approach to finding the Earth's circumference by Eratosthenes, who a century earlier arrived at a figure of 252,000 stadia; both men's figures for the Earth's circumference were uncannily accurate.
The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many contexts and justifying the term "the radius of the Earth".
Later arc measurements aimed at determining the flattening of the Earth ellipsoid by measuring at different geographic latitudes. The first of these was the French Geodesic Mission , commissioned by the French Academy of Sciences in 1735–1738, involving measurement expeditions to Lapland ( Maupertuis et al.) and Peru ( Pierre Bouguer et al.).